Researchers suspect oil affect insect life

Preliminary results from field work and lab tests indicate two oil components - naphthalene and methylnaphthlane - are at least partly responsible for declines in insect populations in coastal marshes affected by the 2010 BP oil spill, LSU researcher Linda Hooper-Bui tells The Advocate (http://bit.ly/11Zhavr).

The mystery is why the compounds are increasing, she said.

"We have results, good information, that these are increasing and that this is an emerging problem," Hooper-Bui said of the two compounds.

LSU professor Eugene Turner said the compounds are aromatics that should be venting into the atmosphere. Instead, some process is creating more of them in the soil than is being allowed to be released, he said.

In addition, Turner said, the problem is being found not just in heaviest-oiled areas but also in areas affected by small amounts.

Although preliminary results point to the two compounds but research continues, he said.

"We're still teasing this out," said LSU coastal expert Ed Overton. "We're a long way from figuring this thing out."

Hooper-Bui said the two compounds suspected as the cause for the decline in insect populations in the coastal marshes are known to be insecticides. She said they are widely used in mothballs because their toxicity to insects.

Hooper-Bui and a number of other researchers from LSU and other universities have been looking at ecosystemwide potential impacts from the Deepwater Horizon disaster in 2010 as part of the Coastal Water Consortium. Funding for the work has come from the National Science Foundation, the Northern Gulf Institute, the Gulf of Mexico Research Initiative and two grants from LSU.

Part of Hooper-Bui's work was to look at the impact to insects and spiders but because they are an important part of the coastal marsh food chain.

Some insects were disappearing that didn't have much contact with sediment or water in the marsh so the researchers set up a field experiment. Crickets were placed in small cages with food and water and then floated in a cage on the marsh so the only contact they would have with the environment would be the air, she explained.

The crickets in the oiled areas died.

"It was something in the air that was killing them," Hooper-Bui said.

The field work was followed by laboratory tests using sediment collected in 2011 and again, the crickets died.

More recently, the lab experiment was repeated for soil collected in March 2013, and the crickets on that soil again died, she said.

There were other signs of something is wrong within the more than 100 insects and spiders the researchers examined.

One example is the population decline of ants that live in the hollow stems of marsh grass starting in 2010.

"By March 2012, we were extremely hard pressed to see ants in oiled areas," Hooper-Bui said.

In May, the ants had mating flights and she and other researchers tracked where they landed and marked the new colonies to revisit later.

"By July, all of those colonies had disappeared," she said.

Since January, Hooper-Bui and others have been looking for ant colonies in oiled sites but haven't found any yet, she said. Currently, researchers are looking for mating flights of ants in these areas, but haven't found any.